In the field of computing, a database management system (DBMS) is a set of software programs that controls the organization, storage, management, and retrieval of data in a database storage unit. Traditionally, the DBMS is a row-oriented database system; however, there are database systems that are column-oriented. The column-oriented database systems store their content by column rather than by row. This may have advantages for databases, where the aggregates are computed over large numbers of similar data items. A column-oriented implementation of a DBMS would store attributes of a given column in sequence, with the column values for the same column stored in sequence, with the end of one column followed by the beginning of the next column. Column-oriented database systems may be more efficient when an aggregate has to be computed over many rows but only for a smaller subset of all columns of data. This may be so at least because, reading that smaller subset of data can be faster than reading all data. Column-oriented database systems may also be more efficient when new values of a column are supplied for all rows at once, because that column data can be written efficiently and can replace old column data without interfering in any other columns for the rows.